Limbaugh's show reaches 15 - 20 million people weekly across more
than 600 radio stations on which he is syndicated, it is
frequently reported.

Or does it?

We asked Arbitron, the radio ratings measurement service, to give
us data for Limbaugh. This is what spokesperson Kim Myers said:

"Unfortunately, we don't have show specific data for network
programs. The syndicators, Premiere Radio Networks, are the only
ones that have the station clearances. Without that, we can't
figure out the show ratings data."

"If you want to look at the number of different listeners tuning
into Rush's show, you'll want to look at CUME [the cumulative
number of people who listen to the show weekly].Again, the only
place you can get that information is through Premiere Radio
Networks which is based in Los Angeles."

To put that simply, the only reason we "know" that 15 million
people listen to Limbaugh is because the company that gets paid
for syndicating Limbaugh tells us so. A message asking PRN to
explain their methodology was not immediately returned.

"... estimates of Limbaugh's nationwide (and overseas) audience
are exercises in guesswork, slippery methodology and suspect
data. Limbaugh himself has muddied the water with the claim that
he reaches 20 million people a week, although there's no
independent support for that figure."

"Premiere Radio Networks, Limbaugh's national syndicator,
estimated last year that 3.59 million people were in Limbaugh's
audience during an average quarter-hour of his program, based on
a review of Arbitron's piecemeal data about hundreds of
stations."

"Because people typically tune in and tune out of stations,
however, that number doesn't reflect how many individuals
cumulatively listened at some point during the week. What's more,
Premiere's figure is based on data from the first three months of
2008, a virtual lifetime ago in the fast-moving radio business."

"...common industry shorthand to determine the actual size of a
radio audience at any given moment is to cut the cume figure down
by a factor of 10, which would mean Limbaugh's 20 million becomes
2 million. Or, if you take the more modest cume number of 14
million, which some inside the industry have used to judge the
talker's audience, Limbaugh's rating becomes 1.4 million, which
is roughly the same size audience that Rachel Maddow and Keith Olbermann get each night on cable
TV."

So there is it: Absent better data, only 1.4 million people
listen to Limbaugh at any one time.